A massive submarine volcanic eruption that struck southern Japan 7,300 years ago devastated local ecosystems, yet human populations rebounded and grew in surprising regions, according to a study published in Science Advances on October 14, 2026. Researchers from Lunds universitet and the University of Cambridge found that while some Jōmon hunter-gatherer communities vanished or declined sharply after the Kikai-Akahoya eruption, other settlements adapted quickly and expanded despite thick layers of volcanic ash.
Super-Colossal Eruption of Kikai Caldera
The underwater explosion occurred roughly 50 to 60 kilometers south of Kyushu island, leaving behind a submerged caldera measuring about 19 kilometers in diameter. Peter Jordan, lead researcher from Lunds universitet, described the event as a super-colossal eruption rated VEI 7, which ejected nearly 500 cubic kilometers of material. The blast happened without warning, triggering strong earthquakes and massive tsunamis before blanketing the Japanese landscape in deep layers of volcanic ash.
Population Shifts Across Kyushu
Archaeologists previously debated whether the disaster wiped out human habitation across the hardest-hit regions. The new data reveal a much more complex demographic response. In southern Kyushu, the Jōmon population had already been dropping long before the eruption, leaving few residents behind when the volcano blew. Conversely, northern Kyushu experienced population growth before the disaster, a trend that continued straight through the catastrophe as refugees arrived from devastated zones.
Did you know? The Kikai-Akahoya eruption is considered a candidate for the largest Holocene volcanic event on Earth, reshaping coastal geography and forcing inland populations toward northern shores rich in recovering marine resources.
Marine Resource Adaptation and Survival
Interior inhabitants relocated toward the northern coastline where marine ecosystems recovered relatively fast. Enrico Crema of the University of Cambridge noted that while the eruption claimed many lives, survivors migrated, formed new communities, and developed fresh subsistence strategies. By intensifying their exploitation of coastal waters, these groups secured reliable food supplies that supported subsequent population growth.
Questions About Prehistoric Volcanic Impacts
How did inland Jōmon communities survive the ashfall?
Inland groups migrated toward northern coastal areas where quick-recovering marine resources provided a steady food supply after terrestrial ecosystems collapsed.
After a giant eruption 7,300 years ago, some nearby Jomon groups in Japan kept growing.The Kikai-Akahoya blast, from an undersea caldera south of Kyushu, hit southern groups already in decline. Northern Kyushu grew on, likely aided by refugees and the sea (Science Advances).
Why did southern Kyushu have fewer residents during the eruption?
Population numbers in southern Kyushu were already declining long before the Kikai-Akahoya volcano exploded, leaving relatively few people in the immediate disaster zone.
What was the magnitude of the Kikai-Akahoya event?
Researchers estimate the submarine explosion reached a volcanic explosivity index of VEI 7, making it a super-colossal event that ejected nearly 500 cubic kilometers of volcanic material.